Six Glasses

Six identical glasses are placed in a row on the table – first three filled with water, and then three empty ones. Can you move just one glass, so that empty and full glasses alternate?

Take the second full glass, pour all of the water into the second empty glass, and then put it back in its place.

Third Business Day

What is the chance that the third business day of a month is Wednesday?

Assuming there is equal chance that the given month begins with any of the seven days of the week, the answer is 3/7. That’s because Saturday and Sunday are non-working days and therefore if the month starts with any of them, the third business day will be still Wednesday.

Snail on a Tree

A snail is trying to climb a 10-meter poll. Every day it climbs 4 meters up and then during the night slides 3 meters down. How many days are needed for the snail to get to the top of the poll?

Seven days only. After the sixth day, the snail would have climbed 6 meters. During the seventh day, it will climb 4 more meters and will get to the top.

Ping Pong Ball

Your last ping pong ball falls down into a narrow pipe embedded in concrete one foot deep. How can you get it out undamaged if all you have is your tennis paddle, your your shoe-laces, keys, wallet and a plastic water bottle, which does not fit into the pipe?

Using the plastic bottle, pour water into the pipe so that the ball will rise up.

Running Dog

Two people – Mick and Goof, 100 meters apart, start walking towards each other with constant speeds of 2m/s. At the same time Mick’s dog starts running back and fourth between them with constant speed of 6m/s until Mick and Goof meet. How much distance does the dog cover in total?

Mick and Goof will meet after 100/(2 + 2) = 25 seconds. Therefore the dog will run for 25 seconds and will cover 6 x 25 = 150 meters in total.

Four Chains

You have four metal chains and each of them has three links. What is the minimal number of cuts you need to make so that you can connect the chains into one loop with twelve links.

You need only three cuts – cut all of the links of one of the chains and then use them to connect the ends of the remaining three chains.

High Tide

A boat has a ladder with six rungs on it. The rungs are spaced one foot from each other, the lowest one starting a foot above the water. The tide rises with 10 inches every 15 minutes.

How many rungs will be still above the water 2 hours later?

Six rings – the ship and the ladder will be rising with the tide.